Oroville Dam spillway collapse due to “long-term systemic failure”

The Oroville Dam in California suffered from a flawed design and construction, and had inadequate inspections in the decades since it was built in the 1960s. These ongoing errors and omissions, coupled with an overconfident Department of Water Resources created the situation leading to the catastrophic failure of the spillway in Feb. 2017, says an independent report.

The report is blunt. There were multiple problems, made worse by regulators and officials not paying attention. The result was thousands had to be evacuated because of fears the entire dam might fail.

“The seriousness of the weak as-constructed conditions and lack of repair durability was not recognized during numerous inspections and review processes over the almost 50-year history of the project.”

It appears probable, given botched inspections (they were visual only) and maintenance that was never done, that the Division of Safety of Dams will be reorganized.

“This is an institutional failure,” says Ron Stork of Friends of the River, at a recent legislative oversight hearing. “That dam has not been safe since it was constructed.”

Stork is partly referring to the Dept. of Water Resources’ choice to build the dam’s emergency spillway with no concrete reinforcement. Massive erosion on the bare earthen slope is what triggered mass evacuations in February, when weeks of heavy precipitation pushed Oroville Lake over the rim of the spillway, threatening a potentially catastrophic flood.